1. Field of the Invention
The invention relates to a circuit configuration for supplying electrical consumers, in particular sensors in a motor vehicle, with a constant voltage required for their operation.
Such circuit configurations are used in motor vehicles, for instance, in which various control units (for engine control, transmission control, anti-lock and traction control, etc., for instance) cooperate with a great number of sensors. A sensor system with a plurality of external sensors and with digital signal processing for an engine control unit is described in the technical book by Walter Heywang entitled "Sensorik" [Sensor Technology], 3rd Edition, Springer-Verlag, 1988, pp. 252-253.
External sensors often measure ratiometrically. In other words, the ratio between the measurement voltage and the operating voltage is dependent on the measurement variable. The operating voltage for the sensor is made available by the control unit. Since the control unit likewise converts the sensor voltage ratiometrically--the converted measured value is equivalent to the ratio between the measurement voltage and a reference voltage-the sensor operating voltage should be identical to the control unit reference voltage. However, direct derivation of the reference voltage from the control unit for supply to the sensor, while conceivable, is not actually possible, because in automotive engineering, all of the outputs of control units must be protected against short circuits.
With sensor systems known thus far in the industry, every sensor is supplied by a separate voltage controller. The attendant unavoidable difference between the reference voltage of the control unit and the supply voltage of the sensor is expressed as a multiplicative error in the sensor voltage and thus in the outcome of measurement as well.